Spark plug



March 18,1924. 1,481659 R. H. JOHNSON v lSPARK PLUG Filed Feb. l2. 1923 Patented Mar. 18, 1924.

, vUNITED STATES rarest: i

SPARK PLUG.

Application filed' February 12, 1923. Serial No. 618,605.

To all 'whom it may concern? Be it known that I, ROBERT H. JOHNSON, a citizen of the United States, residing at lVashington, in the District of Columbia, have invented certain new and useful Improvements in Spark Plugs; and I do herey declare the followin to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to improve ments 1n spark plugs and has for an object to provide an 'improved plug for use in internal combustion engines which will not foul with carbon and in which the current will be strengthened in order to provide a healthy spark at the gap with consequent economy in fuel and the development of maximum power.

Other objects of the invention are to provide a plug which may be manufactured economically and sold at comparatively low cost on the market, to render the parts of the plug easy to dissemble, thereby permitting of access to the core or insulator and to the spark gap and intensifier for the purpose of adjustment, repair and vreplacement of parts.

With the foregoing and other objects in view, the invention will be more fully described hereinafter, and will bemore particularly pointed out in the claims appended hereto.

In the drawings, wherein like symbols refer to like orcorresponding parts throughout the sevral views,

Figure l is a side view of an improved spark plug constructed according to the present invention.

Figure 2 is a longitudinal section through the plug.

Figure 3 is a cross section taken on the line 3 3 in Figure 2.

Figure 4 is also a cross section taken on the line 4-4 in Figure 2. i

Figure 5 is another cross section taken on the line 5-5 also in Figure 2, and

Figure 6 is a fragmentary section taken longitudinally through the lower portion of the plug showing the cleaning plunger in the raised position.

Referring more particularly. to the drawings, 1 designates the shell having the threaded shank 2 to enable it to be screwed into the head or cylinder-of an internal combustion engine in accordance with a well known manner. The upper portion of the shell 1 is made hexagonal as indicated at 3 to receive a wrenchorl other implement forturning the shell. lVithin the shell is au internal shoulder Il adapted to cooperate with a similar shoulder upon the lower sec tion 5 of the insulator or core. The lower portion or stein offthis section 5 is provided with a cylindrical or other recess 6 opening upon ,the base of the core and adapted toreceive acleaning plunger which embraces the central positive electrode7. This posithe recess 6 and slightly beneath the lower tive electrode extends down axially through end of the porcelain where it forms a spark gap with the negative electrode 8, grounded upon the shell 2 and in this instance being carried by a side portion of the yoke 9 which extends substantially diametrically 'fromvv one side of the lower yportion of the shell to the other, the yoke being curved in order to remove its intermediate part from interference with the electrodes or spark gap.

A porcelain or other insulating pad '10 is carried by the intermediate part of the yokev 9 in position to act as a stop for the lower end of the cleaning plunger. This cleanin plunger is composed of a cylindrical .barre 11 fitting .the rod electrode 7 whereby to slide thereon freely back and forth. A flange 12 extends out radially from the upper end of the barrel 11 and a ring 13 is carried by the outer end of the flange, this ring being arranged at right angles to the flange or concentric with the barrel 11. The ring lits the interior wall of the recess 6. The lower end of the barrel is slotted as indicated at 14 leaving teethy 15 between the slots adapted to scrape the carbon from the electrodes and to permit passage of the spark through the slots 14.

The upper end of the positive electrode 7 extends above the lower section 5 of the insulator and' one or more radial arms 16, extending from thev rod electrode `are embedded in the porcelain to prevent creeping' of the electrode axially which would disar-v range the placing of the spark gap and the intensifier gap. Of course the electrode can also be cemented in the porcelain.

Said upper end of the electrodei7 lies` `forcing the insulator parte together and i vagain-st the shoulder l in the shell without danger of injury or breakage in the core. Noni the chamber Y17 is adapted-to com;

municate with the yatmosphere bv one or .free at the spark gap.

more ports 27 arranged diagonally and ex- ;tending from the upper portion of said; chamber. 'lheintensiiier gap is thus per-Y initted torbreathe.7 Into the upper portion of the chamber 17 projects an intermediate electrode 28 having a T-shaped-` head 29 embedded in the poacelain material and having the opposite branches of itsfhead connected to theY wires 30 and 81 which are arranged Yin the passage 32 extending down axial] through the upper core section 18. In this core section is also disposed a magnet 33 or a stripr of soft iron or otherappropriate material being bent intoy the shape of a horseshoe and resting upon a supporting wall 34 of the insulating material which projects into the passage 32. The wires are 'p wound a number of turns about opposite sides or poles of the soft Viron bar and the magnetic fiux or field set up wiil tend Vto retard-the current or interpose a resistance which will intensify the spark leaping across the spark gap. The upper end of the wires are twisted together and arranged with the inverted T-head 35 upon the threaded binding post 36 which projects above the insulator and receives the binding nuts 37 and 38 by which the lead Wire is coupled to the electrode.

Inthe use of the plug, vthe engine on its compression stroke wiil drive the cleaning plunger to the upper position shown in Figure G, thus leaving the electrodes entirely lVhen the circuit is closed at the end of the compression stroke. the spark lreinforced by the magnet coils and by the intensifier gap, will leap across the electrodes serve to ignite thoroughly and completely the compressed charge. .Xs-the piston desi-ends on its suction stroke, the cleaning plunger will be drawn down to the position indicated in Figure 2 and its movement will scrape any carbon deposits from the lower portion of the positive electrode and also keep any carbon from bridging spark gap. At the same time the ring 13 will scrape the Walls' of the Lrecess and avoid the formation of' carbon at this point so as to avoid short cireuitingY of the gap. The teeth 15 are peculiarly adapted for scraping the carbon and at the same time theslots 14 permit of the passage of the spark across the gap should the cleaning plunger for any reason be down when the current is turned through theplug. i i

Should the lower section 5 of the insulator become cracked because of the high temperature or damaged for any other reason, the nut 25 niay'berem'oved and the sections of the insulator taken out of the shell and separated, the damaged sectionY being discarded in favor of a fresh one. The cleaning pluriger may be slipped off the electrode and insert-ed upon the electrode of the fresh seetion so that this )art need not be re laced.

l .Y Y

In a similar manner if the upper sectionis injured. This may be replaced without requiring the expense of replacing thelower section and its parts. Y

' It is obvious that various changes and modifications may be made in the details 0f construction and design of the above specifically described embodiment of this invention without departing from the spirit there-p of, such changes and modications being restrictedronly by: the scope of the following claims Y f if Y;

What I claim is i'. A spark plug comprising a shell, an nsulator therein having a recess in its lower endE a positive electrode carried by the insulator and projecting through said recess, a negative electrode cooperating with said positive electrode and grounded on said shell, a plunger mounted to reciprocate in said recess and to scrape the carbon therefrom, said plunger also vslidably iitted above the positive electrode and having slots at its base with teeth formed between the slots, and a yoke beneath the spark gap to arrest the movement of the plunger. 5

2. A spar-k plug comprising a shell, an insulator therein having a recess in its lower end, a positive electrode in the insulator eX- tcnding into the recess, a negative electrode spaced at the side of the lpositive electrode, a plunger movably mounted in the recess and connliosed of a barrel sliding on the positive electrode, a Aliangc on the upper end of the barrel, and a ring carried by the flange and wiping the wall of tlu` recess, a yoke carried by the shell beneath the spark gap and having an insulating pad in the path of said barrel. 

